Pre-release plastic packaging of MEMS and IMEMS devices
First Claim
1. A method for activating at least one sensitive area of a microelectronic device, comprising:
- providing a microelectronic device comprising a sensitive area disposed on a substrate, wherein the sensitive area comprises an inner surface facing towards the substrate and an outer surface facing away from the substrate; and
wherein the microelectronic device further comprises a layer of electrically insulating material disposed on and touching said outer surface of the sensitive area, wherein the outer surface of the sensitive area is covered and protected by the electrically insulating material; and
then perforating a sufficient amount of the layer of electrically insulating material to expose at least part of the outer surface of the sensitive area to the surrounding environment by using a non-ablative material removal process to selectively remove some, but not all, of the layer of electrically insulating material;
whereby said at least part of the outer surface of the sensitive area becomes activated by exposing said at least part of the outer surface of the sensitive area to the surrounding environment.
3 Assignments
0 Petitions
Accused Products
Abstract
A method is disclosed for pre-release plastic packaging of MEMS and IMEMS devices. The method can include encapsulating the MEMS device in a transfer molded plastic package. Next, a perforation can be made in the package to provide access to the MEMS elements. The non-ablative material removal process can include wet etching, dry etching, mechanical machining, water jet cutting, and ultrasonic machining, or any combination thereof. Finally, the MEMS elements can be released by using either a wet etching or dry plasma etching process. The MEMS elements can be protected with a parylene protective coating. After releasing the MEMS elements, an anti-stiction coating can be applied. The perforating step can be applied to both sides of the device or package. A cover lid can be attached to the face of the package after releasing any MEMS elements. The cover lid can include a window for providing optical access. The method can be applied to any plastic packaged microelectronic device that requires access to the environment, including chemical, pressure, or temperature-sensitive microsensors; CCD chips, photocells, laser diodes, VCSEL'"'"'s, and UV-EPROMS. The present method places the high-risk packaging steps ahead of the release of the fragile portions of the device. It also provides protection for the die in shipment between the molding house and the house that will release the MEMS elements and subsequently treat the surfaces.
226 Citations
88 Claims
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1. A method for activating at least one sensitive area of a microelectronic device, comprising:
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providing a microelectronic device comprising a sensitive area disposed on a substrate, wherein the sensitive area comprises an inner surface facing towards the substrate and an outer surface facing away from the substrate; and
wherein the microelectronic device further comprises a layer of electrically insulating material disposed on and touching said outer surface of the sensitive area, wherein the outer surface of the sensitive area is covered and protected by the electrically insulating material; and
thenperforating a sufficient amount of the layer of electrically insulating material to expose at least part of the outer surface of the sensitive area to the surrounding environment by using a non-ablative material removal process to selectively remove some, but not all, of the layer of electrically insulating material;
whereby said at least part of the outer surface of the sensitive area becomes activated by exposing said at least part of the outer surface of the sensitive area to the surrounding environment.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
providing a microelectronic device comprising a sensitive area disposed on a substrate, wherein the sensitive area comprises an inner surface facing towards the substrate and an outer surface facing away from the substrate; and
thendepositing a layer of electrically insulating material on and touching said outer surface of the sensitive area, wherein the outer surface of the sensitive area becomes covered and protected by the layer of electrically insulating material.
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38. The method of claim 37, wherein the insulating material comprises a flowable dielectric compound selected from epoxy resin, silicone, rubber, thermosetting plastic, thermoplastic plastic, two-part epoxy, UV-curable epoxy, anhydride epoxy, polyimide epoxy, polyphenylene sulfide polymer, polyetherimide polymer, polyethersulfone polymer, liquid crystal polymer, urethane, and polyester resin.
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39. The method of claim 37, wherein the insulating material comprises glass.
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40. The method of claim 37, wherein the covering step comprises using a process selected from pouring, casting, spin-on coating, and glob top molding.
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41. The method of claim 37, wherein the covering step comprises encapsulating the device in the electrically insulating material.
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42. The method of claim 41, wherein the microelectronic device comprises an unreleased MEMS device wirebonded to a lead frame, and further comprising a MEMS element located within the sensitive area.
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43. The method of claim 41, further comprising releasing the unreleased MEMS element, after completing the perforation step.
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44. The method of claim 41, wherein the microelectronic device comprises an unreleased MEMS device flip-chip mounted to a lead frame;
- and further comprising a MEMS element located within the sensitive area.
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45. The method of claim 41, wherein the encapsulating step comprises transfer molding with at least a two-piece mold having an upper mold part and a lower mold part.
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46. The method of claim 45, wherein the transfer molding step further comprises using exclusionary means located inside of the closed mold to prevent the insulating material from flowing into a volume positioned above, but not touching, the sensitive area;
- whereby a substantially empty void is created inside of the volume after removing the exclusionary means and the device from the mold; and
further wherein the exclusionary means allows some insulating material to flow across the sensitive area during the transfer molding step, thereby creating a locally thinner region of encapsulant directly above, and in contact with, the sensitive area.
- whereby a substantially empty void is created inside of the volume after removing the exclusionary means and the device from the mold; and
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47. The method of claim 46, wherein the exclusionary means comprises an inwardly extending integral protrusion belonging to the upper mold part, which extends towards the surface of the sensitive area, but does not touch it.
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48. The method of claim 46, wherein the exclusionary means comprises a separate mold insert member removeably attached to the inside surface of the upper mold part, which extends towards the surface of the sensitive area, but does not touch it.
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49. The method of claim 37, wherein the electrically insulating material comprises a flowable dielectric compound selected from the group consisting of a resin, a plastic, a glob-top polymer, a gel, a fast curing epoxy, a slow curing epoxy, a water-soluble compound, a NOVOLAC™
- epoxy, a hardenable resin, and a transparent resin.
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50. The method of claim 1, wherein the electrically insulating material comprises a water-soluble material, and further wherein the non-ablative material removal process comprises using water as an etching fluid.
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51. A method for activating at least one sensitive area of a microelectronic device, comprising:
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providing a microelectronic device having a sensitive area covered by a temporary protective material;
wherein the temporary protective material is substantially encased in an electrically insulating material that is different than the temporary protective material;
perforating the electrically insulating material to provide access to the temporary protective material; and
removing the temporary protective material by using a non-ablative material removal process;
whereby the sensitive area becomes activated by being exposed to the surrounding environment. - View Dependent Claims (52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68)
providing a microelectronic device having a sensitive area;
covering at least the sensitive area in a temporary protective material;
substantially encasing the temporary protective material with an electrically insulating material that is different than the temporary protective material; and
substantially hardening the electrically insulating material before perforating the electrically insulating material.
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53. The method of claim 52, wherein the encasing step comprises encapsulating the device in the electrically insulating material.
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54. The method of claim 52, wherein the encasing step comprises using a process selected from pouring, casting, spin-on coating, and glob top overmolding.
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55. The method of claim 52, wherein the microelectronic device comprises a wafer having a plurality of sensitive areas disposed thereon;
- and further wherein the covering step comprises covering the plurality of sensitive areas; and
further comprising a step of cutting the wafer into individual device dies before performing the encasing step.
- and further wherein the covering step comprises covering the plurality of sensitive areas; and
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56. The method of claim 51, wherein the temporary protective material comprises a flowable elastomeric material selected from rubber, silicone, and polyurethane.
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57. The method of claim 56, wherein the step of removing the temporary protective material comprises picking the material out by hand or by a robot manipulator.
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58. The method of claim 51, wherein the temporary protective material comprises a dissolvable material.
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59. The method of claim 58, wherein the step of removing the temporary protective material comprises dissolving the material with a solvent that does not substantially dissolve the electrically insulating material.
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60. The method of claim 51, wherein the temporary protective material comprises a low-melting point material.
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61. The method of claim 60, wherein the step of removing the temporary protective material comprises melting the material and letting it flow out.
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62. The method of claim 60, wherein the low-melting point material is a material selected from the group consisting of wax and solder.
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63. The method of claim 51, wherein the electrically insulating material comprises a flowable plastic material that is etchable by nitric acid or fuming nitric acid but is not etchable by sulfuric acid or fuming sulfuric acid.
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64. The method of claim 63, wherein the electrically insulating material comprises an epoxy resin and the temporary protective material comprises a glob top polymer.
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65. The method of claim 51, wherein the electrically insulating material comprises a flowable plastic material that is etchable by sulfuric acid or fuming sulfuric acid but is not etchable by nitric acid or fuming nitric acid.
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66. The method of claim 65, wherein the electrically insulating material comprises a glob top polymer and the temporary protective material comprises an epoxy resin.
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67. The method of claim 51, wherein the temporary protective material is selected from parylene, silicon nitride, metal, a vapor deposited organic material, cynoacrylate, a carbon film, a self-assembled monolayered material, perfluoropolyether, hexamethyidisilazane, or perfluorodecanoic carboxylic acid, silicon dioxide, silicate glass, or combinations thereof.
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68. The method of claim 51, wherein the electrically insulating material comprises a water-soluble material, and further wherein perforating the electrically insulating material comprises using water as an etching fluid.
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69. A method for activating at least one sensitive area of a microelectronic device, comprising, in the order presented:
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a) providing a microelectronic device comprising a sensitive area disposed on a substrate, wherein the sensitive area comprises an inner surface facing towards the substrate and an outer surface facing away from the substrate; and
wherein the microelectronic device further comprises a layer of electrically insulating material disposed on and touching said outer surface of the sensitive area, wherein the outer surface of the sensitive area is covered and protected by the electrically insulating material;
b) performing at least one packaging step; and
c) perforating a sufficient amount of the layer of electrically insulating material to selectively expose at least part of the outer surface of the sensitive area to the surrounding environment by using a non-ablative material removal process to remove some, but not all, of the layer of electrically insulating material;
whereby said at least part of the outer surface of the sensitive area becomes activated by exposing said at least part of the outer surface of the sensitive area to the surrounding environment.
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70. A method for activating at least one sensitive area of a microelectronic device, comprising, in the order presented:
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a) providing a microelectronic device comprising a sensitive area disposed on a substrate, wherein the sensitive area comprises an inner surface facing towards the substrate and an outer surface facing away from the substrate; and
wherein the microelectronic device further comprises a first layer comprising a temporary protective material disposed on and touching said outer surface of the sensitive area, wherein the outer surface of the sensitive area is covered and protected by the temporary protective material; and
further wherein the temporary protective material is substantially encased in a second layer comprising an electrically insulating material that is different than the temporary protective material;
b) perforating a sufficient amount of the second layer of electrically insulating material to provide access to the first layer of temporary protective material; and
c) exposing at least part of the outer surface of the sensitive area to the surrounding environment by using a non-ablative material removal process to selectively remove at least some of the first layer of temporary protective material;
whereby said at least part of the outer surface of the sensitive area becomes activated by exposing said at least part of the outer surface of the sensitive area to the surrounding environment.
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71. A method for activating at least one sensitive area of a microelectronic device, comprising, in the order presented:
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a) providing a microelectronic device comprising a sensitive area disposed on a substrate, wherein the sensitive area comprises an inner surface facing towards the substrate and an outer surface facing away from the substrate;
b) applying a temporary protective material on and touching said outer surface of the sensitive area;
c) performing at least one packaging step;
d) substantially encasing the temporary protective material in a second layer comprising an electrically insulating material that is different than the temporary protective material;
e) perforating a sufficient amount of the second layer of electrically insulating material to provide access to the first layer of temporary protective material; and
f) exposing at least part of the outer surface of the sensitive area to the surrounding environment by using a non-ablative material removal process to selectively remove at least some of the first layer of temporary protective material;
whereby said at least part of the outer surface of the sensitive area becomes activated by exposing said at least part of the outer surface of the sensitive area to the surrounding environment.- View Dependent Claims (72, 73, 74, 75, 76, 77, 78)
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79. A method of packaging a MEMS device, comprising, in the order presented:
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a) providing a wafer comprising a plurality of unreleased MEMS devices fabricated on the wafer;
b) releasing the MEMS elements;
c) applying a first layer comprising a temporary protective material to the released MEMS elements;
d) singulating the wafer into a plurality of individual dies each comprising a MEMS device covered by the temporary protective material;
e) attaching the die and wirebonding the MEMS device;
f) substantially encasing at least the temporary protective material in a second layer comprising an electrically insulating material that is different than the temporary protective material;
g) perforating a sufficient amount of the second layer of electrically insulating material to provide access to the first layer of temporary protective material, while not removing electrically insulating material from the wirebonds; and
h) exposing and releasing the temporarily protected MEMS elements by using a non-ablative material removal process to selectively remove the temporary protective material;
thereby activating the MEMS device.- View Dependent Claims (80, 81, 82, 83, 84, 85, 86, 87, 88)
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Specification